High speed AC input sensor conversion

ABSTRACT

A system for determining an amplitude of a sinusoidal output waveform from a sensor includes a controller configured to provide a sample signal having a sample frequency that is four times a frequency of a sinusoidal excitation waveform provided to the sensor. The sensor has inductively-coupled primary and secondary windings that produce the sinusoidal output waveform from the secondary winding when the excitation waveform is provided to the primary winding. An analog-to-digital converter measures a first and second voltage of the sensor waveform separated in time by the period of the sample frequency, and the system calculates the amplitude based on the measurements of the first and second voltages.

CROSS-REFERENCE TO RELATED APPLICATION(S)

Reference is hereby made to U.S. patent application Ser. No. 16/246,956,entitled “HIGH SPEED AC SENSOR PHASE MEASUREMENT”, which is filed on thesame date as this application.

BACKGROUND

The present disclosure relates to electronic measurement circuits, andmore particularly, to high-speed electronic measurement circuits fordetermining the voltage and the phase shift of an AC signal.

Resolvers, linear variable differential transformers (LVDTs), andproximity sensors are commonly used to determine the position of movablecomponents in machinery, control systems, and the like. For example,resolvers are oftentimes associated with starter motor generators andactuators in aircraft to provide feedback regarding the state of theactuator, e.g., whether the actuator is open, partially open, or closed.A typical resolver includes a primary winding and at least one secondarywinding, rotatable with respect to the primary winding. In otherapplications, such as mechanical control systems, LVDTs are used todetermine the linear position of linearly moving components. Forexample, LVDTs are oftentimes associated with fuel racks on gas turbineengines to provide feedback regarding the state of the fuel controlvalves, e.g., whether the valve is open, partially open, or closed. Atypical LVDT includes a primary winding, at least one secondary winding,and a linearly movable ferromagnetic core that alters the mutualinductive coupling between the primary the secondary winding(s). In yetother applications, proximity sensors can be used to determine theproximity of a target to a source component, with a primary winding oneither the target or the source, and the secondary winding on the other.

Resolvers, LVDTs, and proximity sensors are related in that a sinusoidalwaveform is typically applied to a primary coil, thereby inducing asecondary voltage in the one or more secondary coils through mutualinductive coupling between the primary and the secondary windings. Theamplitude and/or phase of the induced secondary voltage can beindicative of a relative position between the primary and secondarywindings, and/or of a position of a moveable magnetic core that affectsthe mutual inductive coupling. Many resolver, LVDT, and proximity sensoralgorithms require a full cycle of the sinusoidal waveform to determinethe amplitude of the induced secondary voltage. Moreover, many resolver,LVDT, and proximity sensor algorithms require more than a full cycle ofthe induced secondary voltage to calculate the phase shift, because thealgorithm requires the detection of zero crossings.

Advanced systems are dependent on highly-responsive sensor systems foroptimum functioning. Accordingly, it would be beneficial to provideimproved interfaces for resolvers, LVDTs, and proximity sensors that canprovide a high-speed measurement of the voltage and/or phase of theinduced secondary voltage in less than half of a waveform cycle.

SUMMARY

A system for determining an amplitude of a sinusoidal output waveformfrom a sensor includes a controller configured to provide a samplesignal having a sample frequency that is four times a frequency of asinusoidal excitation waveform provided to the sensor, measure a firstvoltage of the sinusoidal output waveform and a second voltage of thesinusoidal output waveform via an analog-to-digital converter (ADC), thesecond voltage measurement occurring at a time corresponding to a periodof the sample frequency following the first voltage measurement, andcalculate the amplitude of the sinusoidal output waveform based on themeasurements of the first and second voltages. The sensor includes aprimary winding configured to receive the sinusoidal excitation waveformand a secondary winding that is inductively coupled to the primarywinding and is configured to produce the sinusoidal output waveform whenthe sinusoidal excitation waveform is provided to the primary winding.

A method of using an electronic circuit to determine an amplitude of asinusoidal waveform includes providing by a controller an excitationsignal having an excitation frequency to an exciter, providing by thecontroller a sample signal having a sample frequency that is four timesthe excitation frequency to an analog-to-digital converter (ADC),supplying by the exciter a sinusoidal excitation waveform having theexcitation frequency to a primary winding, measuring by the ADC a firstvoltage of the sensor waveform and a second voltage of the sensorwaveform, the second voltage measurement occurring at a timecorresponding to the period of the sample frequency following the firstvoltage measurement, and calculating by the controller the amplitudebased on the measurements of the first and second voltage. The primarywinding is inductively coupled to a secondary winding, the secondarywinding is configured to produce a sensor waveform when the sinusoidalexcitation waveform is supplied to the primary winding, and thesecondary winding is configured to input the sensor waveform to an ADC.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic block diagram of a voltage measurement system ofthe prior art.

FIG. 2 is a schematic block diagram of a phase measurement system of theprior art.

FIG. 3 is a schematic block diagram of a high-speed AC voltage sensor.

FIG. 4 is a schematic block diagram of a high-speed AC phase sensor.

FIG. 5 is a pair of waveforms depicting the voltage and phasemeasurements in the high-speed AC voltage sensor and high-speed AC phasesensor.

DETAILED DESCRIPTION

The present disclosure provides high-speed electronic measurementcircuitry that can determine the voltage and phase shift of an AC signalusing two samples of a sinusoidal waveform spaced π/2 radians (i.e., 90deg.) apart. The circuitry can apply trigonometric substitutions to thesamples, and determine the amplitude of the measured waveform. Thecircuitry can calculate the root-mean-square (RMS) value of the waveformfrom the determined amplitude. This can provide a rapid determination ofthe RMS value of an AC signal in less than a half-cycle. Relatedcircuitry can provide a rapid determination of a phase shift in lessthan a half-cycle. An appreciation of the present disclosure is bestobtained by having an understanding of the prior art.

FIG. 1 is a schematic block diagram of a voltage measurement system ofthe prior art. Shown in FIG. 1 are voltage measurement system 10,electronic control 12, controller 14, exciter 16, analog-to-digitalconverter (ADC) 18, sensor 24, primary winding 26, and secondary winding28. Electronic control 12 includes controller 14, exciter 16, and ADC18. Controller 14 provides a signal to exciter 16, in turn producing asinusoidal waveform that is applied to sensor 24. Sensor 24 can be aresolver, linear variable differential transformer (LVDT), proximitysensor, or other sensor type having primary winding 26 and secondarywinding 28. Mutual inductive coupling between primary winding 26 andsecondary winding 28 cause a voltage to be induced in secondary winding28, which is input to ADC 18. The digital output of ADC 18 is input toand processed by controller 14. Typical methods of determining theamplitude of the secondary voltage from secondary winding 28 includeoversampling the secondary voltage and determining the location of thesignal peak by using a zero-crossing detector. A fast Fourier transform(FFT) can also be utilized as a digital signal processing technique. Theaforementioned methods typically require at least a full cycle of asinusoidal waveform to accomplish, and some systems can require two ormore waveform cycles. While voltage measurement system 10 can provide anadequate level of performance in systems where the parameter beingmeasured changes slowly relative to the period of the sinusoidalwaveform, system response can be too slow for rapidly-changingparameters.

FIG. 2 is a schematic block diagram of a phase measurement system of theprior art. Shown in FIG. 2 are phase measurement system 30, electroniccontrol 32, controller 34, exciter 36, exciter zero-crossing detector(ZCD) 40, sensor ZCD 42, sensor 44, primary winding 46, and secondarywinding 48. Phase measurement system 30 can be used to measure the phaseshift between a primary signal and a secondary signal, for example, insystems described above in regard to FIG. 1. Electronic control 32includes controller 34, exciter 36, exciter ZCD 40, and sensor ZCD 42.Controller 34 provides a signal to exciter 36, in turn producing asinusoidal waveform that is applied to sensor 44. Sensor 44 can be aresolver, LVDT, or proximity sensor, having primary winding 46 andsecondary winding 48. Mutual inductive coupling between primary winding46 and secondary winding 48 cause a voltage to be induced in secondarywinding 48, which is input to sensor ZCD 42. Controller 34 receives andcompares the outputs of exciter ZCD 40 and sensor ZCD 42, therebycalculating the phase shift between exciter 36 output (i.e., thewaveform applied to primary winding 46) and the waveform that is inducedin secondary winding 48. A measurement of the phase shift can be used todetermine a rotary position of a resolver, for example. Theaforementioned method typically requires at least a full cycle of asinusoidal waveform to accomplish, and some systems can require two ormore waveform cycles. While phase measurement system 30 can provide anadequate level of performance in systems where the parameter beingmeasured changes slowly relative to the period of the sinusoidalwaveform, system response can be too slow for rapidly-changingparameters. A rapid phase shift can also provide an indication of afailure of sensor 44. Determination of a failure of sensor 44 withinone-to-two waveform cycles can be acceptable in some situations,although a faster response can be beneficial in other situations.

FIG. 3 is a schematic block diagram of a high-speed AC voltage sensor.Shown in FIG. 3 are high-speed voltage sensor 100, electronic control102, controller 104, fundamental frequency signal 106 having fundamentalfrequency (f), 4× fundamental frequency signal 108 having frequency 4f,exciter 110, exciter output 112, ADC 114, ADC output 116, secondarywinding output 118, sensor 124, primary winding 126, and secondarywinding 128. Electronic control 102 includes controller 104, exciter110, ADC 114, and ADC output 116. Electronic control 102 can be referredto as an electronic circuit. Sensor 124 can be a resolver, LVDT,proximity sensor, or other sensor type having primary winding 126 andsecondary winding 128. Primary winding 126 can include one or morecoils, and/or secondary winding 128 can include one or more coils.Mutual inductive coupling between primary winding 126 and secondarywinding 128 cause a voltage to be induced in secondary winding 128, withthe mutual inductive coupling being influenced by one or more measurableparameters. In one embodiment, for example, the position of one or moresecondary windings 128 relative to primary winding 126 can induce avarying voltage and/or phase shift in secondary winding 128. In anotherembodiment, the position of a moveable ferromagnetic core (not shown)near sensor 124 can induce a varying voltage and/or phase shift insecondary winding 128. In yet another embodiment, the physicalseparation between primary winding 126 and secondary winding 128 caninduce a varying voltage and/or phase shift in secondary winding 128.

Referring again to FIG. 3, controller 104 produces two frequencies:fundamental frequency (f) and 4× fundamental frequency (4f). Fundamentalfrequency (f) can also be referred to as the excitation frequency (f),and 4× fundamental frequency (4f) can be referred to as the samplefrequency. In the illustrated embodiment, the excitation frequency canbe between 2,000-3,500 Hz. The relationship between excitation frequency(f) and the period (T) of the excitation waveform is given by:

$\begin{matrix}{T = \frac{1}{f}} & {{Equation}\mspace{14mu} 1}\end{matrix}$

For example, if excitation frequency (f) is 2,500 Hz (i.e., 2.5 KHz),then period (T) is 0.0004 sec (i.e., 0.4 msec).

Referring again to FIG. 3, controller 104 drives exciter 110 atfundamental frequency (f), and exciter 110 in turn applies excitationvoltage (V_(E)) 112 to primary winding 126, thereby inducing secondaryvoltage (V_(S)) in secondary winding 128 and provided as secondarywinding output 118. Secondary winding output 118 provides secondaryvoltage (V_(S)) as an input to ADC 114. Secondary winding output 118 canalso be referred to as input voltage, because it is an input toelectronic control 102. It is to be appreciated that excitation voltage(V_(E)) and/or secondary voltage (V_(S)) can be written with or withoutthe use of a subscript (i.e., V_(E) or VE, and V_(S) or VS,respectively), while having the same meaning within the scope of thepresent disclosure. ADC 114 also receives an input of 4× fundamentalfrequency signal 108 from controller 104. The time period between twoconsecutive cycles of 4× fundamental frequency signal 108 is T/4, whereT is the period of the excitation waveform. ADC 114 takes twoconsecutive samples of secondary voltage (V_(S)) spaced T/4 apart,providing ADC output 116 to controller 104. Referring again to theprevious example, if excitation frequency (f) is 2,500 Hz, then period(T) is 0.4 msec, and T/4 is 0.1 msec. Because secondary voltage (V_(S))is a sinusoidal waveform, the period between two consecutive samples ofsecondary voltage (V_(S)) can be expressed as π/2 rad., or 90 deg.

From taking two samples π/2 rad. apart, the root-mean-square (RMS)voltage of a sinusoidal waveform can be expressed as:

$\begin{matrix}{V_{RMS} = \sqrt{\frac{\left( {{V_{PK}\left( {\sin(x)} \right)}^{2} + {V_{PK}\left( {\sin\left( {x + \frac{\pi}{2}} \right)} \right)}^{2}} \right)}{2}}} & {{Equation}\mspace{14mu} 2}\end{matrix}$

By applying the trigonometric identity of:

$\begin{matrix}{{\cos(x)} = {\sin\left( {x + \frac{\pi}{2}} \right)}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

Yields the following:

$\begin{matrix}{V_{RMS} = {V_{PK}\sqrt{\frac{\left\lbrack {\left( {\sin(x)} \right)^{2} + \left( {\cos(x)} \right)^{2}} \right\rbrack}{2}}}} & {{Equation}\mspace{14mu} 4}\end{matrix}$

By applying the trigonometric identity of:sin(x)²+cos(x)²=1  Equation 5

Yields the following:

$\begin{matrix}{V_{RMS} = {V_{PK}\sqrt{\frac{1}{2}}}} & {{Equation}\mspace{14mu} 6}\end{matrix}$

As shown with equations 2-5, two samples of secondary voltage (V_(S))taken exactly π/2 rad. apart (i.e., separation in time of T/4) yieldsthe exact measurement of the RMS value of secondary voltage (V_(S)). Itis to be appreciated that equation 6 is also the definition of the RMSvalue of a sinusoidal voltage. Accordingly, high-speed voltage sensor100 can measure secondary voltage (V_(S)) in a time span of T/4 (i.e.,the period corresponding to the sample frequency). Therefore, high-speedvoltage sensor 100 can be used in an embodiment where it can bebeneficial to quickly measure an AC voltage signal and/or quickly detecta change in an AC voltage signal, which can be indicative of a change ina sensor position.

FIG. 4 is a schematic block diagram of the high-speed AC phase sensor.Shown in FIG. 4 are high-speed phase sensor 150, electronic control 152,controller 154, fundamental frequency signal 156 having fundamentalfrequency (f), 4× fundamental frequency signal 158 having 4× fundamentalfrequency (4f), exciter 162, exciter output 164, excitation voltage(V_(E)), exciter ADC 166, exciter ADC output 168, ADC 170, ADC output172, secondary winding output 174, secondary voltage 174, sensor 184,primary winding 186, and secondary winding 188. Electronic control 152includes controller 154, exciter 162, exciter ADC 166, and ADC 170.Electronic control 152 can be referred to as an electronic circuit.Sensor 184 includes primary winding 186 and secondary winding 188, andis substantially as described above with regard to FIG. 3. Controller154 produces two frequencies: fundamental frequency (f), and 4×fundamental frequency (4f). Fundamental frequency (f) can also bereferred to as the excitation frequency. The description of fundamentalfrequency (f), 4× fundamental frequency (4f) (i.e., sample frequency),and the determination of the period (T) of the excitation waveform aresubstantially as described above with regard to FIG. 3.

Controller 154 drives exciter 162 at fundamental frequency (f), andexciter 162 in turn provides exciter output 164 having excitationvoltage (V_(E)) to primary winding 186, thereby inducing secondaryvoltage (V_(S)) in secondary winding 188. Secondary winding output 174provides secondary voltage (V_(S)) as an input to ADC 170. Secondaryvoltage (V_(S)) can also be referred to as input voltage (V_(input))because it is an input to electronic control 152. Exciter 162 alsoapplies excitation voltage (V_(E)) to exciter ADC 166. In theillustrated embodiment, exciter ADC 166 is a four-quadrant (i.e.,wrap-around) ADC-converter, meaning that quadrature values having propersign values are calculated. Exciter ADC 166 can also be referred to as ahigh-speed wrap-around ADC-converter. Exciter ADC 166 and ADC 170 eachreceive 4× fundamental frequency signal 158 having 4× fundamentalfrequency (4f) from controller 154, thereby commanding exciter ADC 166and ADC 170 to each take two consecutive samples at their respectiveinputs separated by timespan T/4, with the first of each sample beingtaken at the same point in time and the second of each sample beingtaken at the same point in time. In particular, exciter ADC 166 takestwo consecutive samples of excitation voltage (V_(E)), and ADC 170 takestwo consecutive samples of secondary voltage (V_(S)). It is to be notedthat excitation voltage (V_(E)) and secondary voltage (V_(S)) have thesame frequency (i.e., fundamental frequency (f) having period T).Moreover, because excitation voltage (V_(E)) and secondary voltage(V_(S)) are both sinusoidal waveforms, the angular separation betweentwo consecutive samples taken T/4 apart can be expressed as π/2 rad.(i.e., 90 deg.)

The phase difference (θ_(D)) (i.e., phase shift) between excitationvoltage (V_(E)) and secondary voltage (V_(S)) can be shown through thefollowing series of equations, beginning with the trigonometric identityof equation 3, where x is a voltage measurement at a point:

$\begin{matrix}{{\cos(x)} = {\sin\left( {x + \frac{\pi}{2}} \right)}} & {{Equation}\mspace{14mu} 3}\end{matrix}$

Applying the arctangent (atan) identity:

$\begin{matrix}{\theta = {{atan}\left( \frac{\sin(x)}{\cos(x)} \right)}} & {{Equation}\mspace{14mu} 7}\end{matrix}$

Yields the following identity:

$\begin{matrix}{\theta = {{atan}\left( \frac{\sin(x)}{\sin\left( {x + \frac{\pi}{2}} \right)} \right)}} & {{Equation}\mspace{14mu} 8}\end{matrix}$

The two consecutive samples of excitation voltage (V_(E)) spaced π/2rad. apart are represented as V_(E1) and V_(E2,) respectively.Similarly, the two consecutive samples of secondary voltage (V_(S))(i.e., input voltage (V_(input))) spaced π/2 rad. apart are representedas V_(S1) and V_(S2), respectively. In the illustrated embodiment,electronic control 152 applies a four-quadrant arctangent function. Thefour-quadrant arctangent function can also be denoted as “atan2”. Asused in the present disclosure, “atan” means a four-quadrant (i.e.,atan2 or wrap-around) arctangent value is used. In one particularembodiment, exciter ADC 166 can be a bipolar ADC, thereby being able toconvert positive and negative voltages for proper quadrature operation.In another particular embodiment, exciter ADC 166 can be a unipolar ADCwhile having a bias offset or other appropriate scaling function appliedto its input, thereby being able to provide proper quadrature operation.

Accordingly, by applying the identities of equations 7 and 8, the phasedifference (θ_(D)) between excitation voltage (V_(E)) and secondaryvoltage (V_(S)) can be represented as:

$\begin{matrix}{\theta_{D} = {\left( {{atan}\left( \frac{V_{E1}}{V_{E2}} \right)} \right) - \left( {{atan}\left( \frac{V_{S1}}{V_{S2}} \right)} \right)}} & {{Equation}\mspace{14mu} 9}\end{matrix}$

Therefore, high-speed phase sensor 150 can be used in an embodimentwhere it can be beneficial to quickly measure an AC phase differenceand/or quickly detect a change in an AC phase difference, which can beindicative of a change in a sensor position. In some embodiments, asudden change in an AC phase difference can be indicative of a failedsensor. Therefore, in these embodiments, high-speed phase sensor 150 canrapidly detect the failure of sensor 184, and this rapid detection canoccur more quickly than other detection means. Moreover, becausehigh-speed phase sensor 150 can measure an AC phase difference in a timespan representing ¼ of the AC waveform period, it can be seen that ahigher excitation frequency can result in a shorter measurement timespan.

FIG. 5 is a pair of waveforms depicting the voltage and phasemeasurements in high-speed AC voltage sensor 100 and high-speed AC phasesensor 150 on axes of voltage (V_(E), V_(S)) in volts vs. time inseconds. Shown in FIG. 5 are waveforms 200, excitation voltage (V_(E))waveform 210, secondary voltage (V_(S)) waveform 220, first measurement(t₁) 212, second measurement (t₂) 214, and phase difference (θ_(D)) 222.Period (T) of excitation waveform, and T/4, are both depicted, with Tequating to 2π rad., and T/4 equating to π/2 rad. In the exemplaryembodiment shown in FIG. 5, the peak amplitudes of excitation voltage(V_(E)) and secondary voltage (V_(S)) are normalized for illustrationpurposes. It is to be noted that units of time and voltage are notprovided with waveforms 200.

In the embodiments illustrated above in FIGS. 3-5, the excitationfrequency (f) can be between 2,000-3,500 Hz. For example, in aparticular embodiment, excitation frequency (f) can be 2,500 Hz (i.e.,2.5 KHz). Accordingly, period (T) is 0.4 msec, the measurement frequency10 KHz, and the time span between two voltage measurements is 0.1 msec(i.e., 100 μsec). In some embodiments, excitation frequency (f) canrange between 400-5,000 Hz. In other embodiments, excitation frequency(f) can be less than 400 Hz or greater than 5,000 Hz. It can beappreciated that a higher value of excitation frequency (f) can resultin a shorter time span between two voltage measurements.

In the embodiments illustrated in FIGS. 3-5, the amplitude of excitationvoltage (V_(E)) can be between 5-12 volts peak. In other embodiments,the amplitude of excitation voltage (V_(E)) can be less than 5 voltspeak or greater than 12 volts peak. In the embodiments illustrated inFIGS. 3-5, the amplitude of the secondary voltage (V_(S)) can be between1-5 volts peak. In other embodiments, the amplitude of the secondaryvoltage (V_(S)) can be less than 1 volt peak or greater than 5 voltspeak.

In some of the embodiments illustrated above in FIGS. 3-4, sensor 124,184 can be a resolver that includes a rotatable primary winding, a fixedsecondary winding fixed relative to the rotatable primary winding, and afixed tertiary winding fixed relative to the rotatable primary windingand positioned π/2 radians out of phase with respect to the fixedsecondary winding. The rotatable primary winding can be mechanicallyconnected to a rotating component (not shown). The rotating componentcan rotate completely, either continuously or intermittently. In some ofthese embodiments, the rotating component can rotate in either a forward(clockwise) or a reverse (counter-clockwise) direction. In other ofthese embodiments, the rotating component can rotate in an arc that isless than 2π radians (360 deg.) Non-limiting examples of the rotatingcomponent include a shaft in a gas turbine engine, crankshafts oninternal and external combustion engines, shafts on electromechanicalmachines, synchros, gyrocompasses, dial indicators, and other shafts,dials, rotors, and the like.

In some of the embodiments illustrated above in FIGS. 3-4, sensor 124,184 can be a LVDT that includes a movable ferromagnetic core that ismechanically connected to linearly movable component (not shown) havinga range of motion between about 2.5-5 cm (0.98-1.97 inches). In some ofthese embodiments, the linearly movable component can have a range ofmotion that is less than 2.5 cm (0.98 inches). In other of theseembodiments, the linearly movable component can have a range of motionthat is greater than 5 cm (1.97 inches). In yet other of theseembodiments, the linearly movable component can have a range of motionthat is greater than 25 cm (9.84 inches). Non-limiting examples of alinearly movable component include a linear component in a gas turbineengine and any linearly movable mechanism on any mechanical orelectromechanical component or system.

In some of the embodiments illustrated above in FIGS. 3-4, sensor 124,184 can be a proximity sensor that is configured to determine theproximity of a source (not shown) to a target (not shown). In some ofthese embodiments, the proximity detection range can be between 2.5-10cm (0.98-3.94 inches). In other of these embodiments, the proximitydetection range can be between 1-25 cm (0.39-9.84 inches). In yet otherof these embodiments, the proximity detection range can be less than 1cm (0.39 inch) or more than 25 cm (9.84 inches). Non-limiting examplesof applications of a proximity sensor include gas turbine engines,fixed- and rotary-wing aircraft, aircraft handling and maintenanceequipment, process control systems, and factories.

In the embodiments illustrated above in FIGS. 3-5, it should beunderstood that the computing algorithms that are performed bycontrollers 104, 154 can be implemented in digital logic or by aprocessor, and can involve computing in-phase and quadrature-phaseresultants of the sampled excitation and secondary voltages. Further, itshould also be noted that a computing device can be used to implementvarious functionality, such as that attributable to the method ofdigital demodulation and other functions performed by afield-programmable gate array (FPGA). In terms of hardware architecture,such a computing device can include a processor, a memory, and one ormore input and/or output (I/O) device interface(s) that arecommunicatively coupled via a local interface. The local interface caninclude, for example but not limited to, one or more buses and/or otherwired or wireless connections. The local interface may have additionalelements, which are omitted for simplicity, such as controllers, buffers(caches), drivers, repeaters, and receivers to enable communications.Further, the local interface may include address, control, and/or dataconnections to enable appropriate communications among theaforementioned components.

The aforementioned processor can be a hardware device for executingsoftware, particularly software stored in memory. The processor can be acustom made or commercially available processor, a central processingunit (CPU), an auxiliary processor among several processors associatedwith the computing device, a semiconductor based microprocessor (in theform of a microchip or chip set), or generally any device for executingsoftware instructions. The memory can include any one or combination ofvolatile memory elements, e.g., random access memory (RAM, such as DRAM,SRAM, SDRAM, VRAM, etc.) and/or nonvolatile memory elements, e.g., ROM,hard drive, tape, CD-ROM, etc. Moreover, the memory may incorporateelectronic, magnetic, optical, and/or other types of storage media. Notethat the memory can also have a distributed architecture, where variouscomponents are situated remotely from one another, but can be accessedby the processor. The software in the memory may include one or moreseparate programs, each of which includes an ordered listing ofexecutable instructions for implementing logical functions. A systemcomponent embodied as software may also be construed as a sourceprogram, executable program (object code), script, or any other entitycomprising a set of instructions to be performed. When constructed as asource program, the program is translated via a compiler, assembler,interpreter, or the like, which may or may not be included within thememory.

The aforementioned I/O devices that may be coupled to system I/Ointerface(s) may include input devices, for example but not limited to,a keyboard, mouse, scanner, microphone, camera, proximity device, etc.Further, the I/O devices may also include output devices, for examplebut not limited to, a printer, display, etc. Finally, the I/O devicesmay further include devices that communicate both as inputs and outputs,for instance but not limited to, a modulator/demodulator (modem) foraccessing another device, system, or network; a radio frequency (RF) orother transceiver; or a telephonic interface, bridge, router, etc. Whenthe computing device is in operation, the processor can be configured toexecute software stored within the memory, to communicate data to andfrom the memory, and to generally control operations of the computingdevice pursuant to the software. Software in memory, in whole or inpart, is read by the processor, perhaps buffered within the processor,and then executed.

Discussion of Possible Embodiments

The following are non-exclusive descriptions of possible embodiments ofthe present invention.

A system for determining an amplitude of a sinusoidal output waveformfrom a sensor, the system comprising a controller configured to: providea sample signal having a sample frequency that is four times a frequencyof a sinusoidal excitation waveform provided to the sensor, the sensorhaving: a primary winding configured to receive the sinusoidalexcitation waveform; and a secondary winding, inductively coupled to theprimary winding, configured to produce the sinusoidal output waveformwhen the sinusoidal excitation waveform is provided to the primarywinding; measure a first voltage of the sinusoidal output waveform and asecond voltage of the sinusoidal output waveform using ananalog-to-digital converter (ADC), the second voltage measurementoccurring at a time corresponding to a period of the sample frequencyfollowing the first voltage measurement; and calculate the amplitude ofthe sinusoidal output waveform based on the measurements of the firstand second voltages.

The system of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

A further embodiment of the foregoing system, wherein the sensor is alinear variable differential transformer (LVDT); and the sensor isconfigured to measure a linear position of a linear componentmechanically connected thereto.

A further embodiment of the foregoing system, wherein the amplitude isrepresentative of the linear position.

A further embodiment of the foregoing system, wherein the sensor is aresolver further comprising a tertiary winding, wherein: the primarywinding is rotatable; the secondary winding is fixed relative to theprimary winding; the tertiary winding is fixed relative to the primarywinding and positioned out of phase with respect to the secondarywinding; and the sensor is configured to measure an angular position ofa rotatable component mechanically connected thereto.

A further embodiment of the foregoing system, wherein the tertiarywinding is positioned π/2 radians out of phase with respect to thesecondary winding.

A further embodiment of the foregoing system, wherein the amplitude isrepresentative of the angular position of the rotary component.

A further embodiment of the foregoing system, wherein the excitationfrequency is between 400-5,000 Hz.

A further embodiment of the foregoing system, wherein the sinusoidalexcitation waveform further comprises a peak amplitude between 5-12volts.

A further embodiment of the foregoing system, wherein the amplitude is aroot-mean-square (RMS) amplitude.

A further embodiment of the foregoing system, further comprising: anexciter, configured to receive the excitation signal from the controllerand to provide to the primary winding the sinusoidal excitation waveformhaving the excitation frequency; the sensor; and the ADC.

A method of method of determining an amplitude of a sinusoidal outputwaveform from a sensor, the method comprising: providing, by acontroller, an excitation signal having an excitation frequency to anexciter; providing, by the controller, a sample signal having a samplefrequency that is four times the excitation frequency, to ananalog-to-digital converter (ADC), supplying, by the exciter, asinusoidal excitation waveform having the excitation frequency to aprimary winding, wherein: the primary winding is inductively coupled toa secondary winding; the secondary winding is configured to produce asensor waveform when the sinusoidal excitation waveform is supplied tothe primary winding; and the secondary winding is configured to inputthe sensor waveform to an ADC; measuring, by the ADC, a first voltage ofthe sensor waveform and a second voltage of the sensor waveform, thesecond voltage measurement occurring at a time corresponding to theperiod of the sample frequency following the first voltage measurement;and calculating, by the controller, the amplitude based on themeasurements of the first and second voltage; wherein the primarywinding and the secondary winding comprise a sensor.

The method of the preceding paragraph can optionally include,additionally and/or alternatively, any one or more of the followingfeatures, configurations and/or additional components:

A further embodiment of the foregoing method, wherein the sensor is alinear variable differential transformer (LVDT); and the sensor isconfigured to measure a linear position of a linear componentmechanically connected thereto.

A further embodiment of the foregoing method, wherein the amplitude isrepresentative of the linear position.

A further embodiment of the foregoing method, wherein the sensor is aresolver further comprising a tertiary winding, wherein: the primarywinding is rotatable; the secondary winding is fixed relative to theprimary winding; the tertiary winding is fixed relative to the primarywinding and positioned out of phase with respect to the secondarywinding; and the sensor is configured to measure an angular position ofa rotatable component mechanically connected thereto.

A further embodiment of the foregoing method, wherein the tertiarywinding is positioned π/2 radians out of phase with respect to thesecondary winding

A further embodiment of the foregoing method, wherein the amplitude isrepresentative of the angular position of the rotary component.

A further embodiment of the foregoing method, wherein the excitationfrequency is between 400-5,000 Hz.

A further embodiment of the foregoing method, wherein the excitationfrequency is between 2,000-3,500 Hz.

A further embodiment of the foregoing method, wherein the sinusoidalexcitation waveform further comprises a peak amplitude between 5-12volts.

A further embodiment of the foregoing method, wherein the amplitude is aroot-mean-square (RMS) amplitude.

While the invention has been described with reference to an exemplaryembodiment(s), it will be understood by those skilled in the art thatvarious changes may be made and equivalents may be substituted forelements thereof without departing from the scope of the invention. Inaddition, many modifications may be made to adapt a particular situationor material to the teachings of the invention without departing from theessential scope thereof. Therefore, it is intended that the inventionnot be limited to the particular embodiment(s) disclosed, but that theinvention will include all embodiments falling within the scope of theappended claims.

The invention claimed is:
 1. A system for determining position of amovable component by calculating an amplitude of a sinusoidal outputwaveform from a sensor, the system comprising a controller configuredto: provide a sample signal having a sample frequency that is four timesa frequency of a sinusoidal excitation waveform provided to the sensor,the sensor having: a primary winding configured to receive thesinusoidal excitation waveform; and a secondary winding, inductivelycoupled to the primary winding in such a manner that the inductivecoupling changes in response to movement of the movable member, thesecondary winding configured to produce the sinusoidal output waveformwhen the sinusoidal excitation waveform is provided to the primarywinding; measure a first voltage of the sinusoidal output waveform and asecond voltage of the sinusoidal output waveform using ananalog-to-digital converter (ADC), the second voltage measurementoccurring at a time corresponding to a period of the sample frequencyfollowing the first voltage measurement; calculate the amplitude of thesinusoidal output waveform based on the measurements of the first andsecond voltages; and determine a position of a movable component basedon the amplitude of the sinusoidal output waveform calculated.
 2. Thesystem of claim 1, wherein: the sensor is a linear variable differentialtransformer (LVDT); and the sensor is configured to measure a linearposition of a linear component mechanically connected thereto.
 3. Thesystem of claim 2, wherein the amplitude is representative of the linearposition.
 4. The system of claim 1, wherein the sensor is a resolverfurther comprising a tertiary winding, wherein: the primary winding isrotatable; the secondary winding is fixed relative to the primarywinding; the tertiary winding is fixed relative to the primary windingand positioned out of phase with respect to the secondary winding; andthe sensor is configured to measure an angular position of a rotatablecomponent mechanically connected thereto.
 5. The system of claim 4,wherein the tertiary winding is positioned π/2 radians out of phase withrespect to the secondary winding.
 6. The system of claim 4, wherein theamplitude is representative of the angular position of the rotarycomponent.
 7. The system of claim 1, wherein the excitation frequency isbetween 400-5,000 Hz.
 8. The system of claim 1, wherein the sinusoidalexcitation waveform further comprises a peak amplitude between 5-12volts.
 9. The system of claim 1, wherein the amplitude is aroot-mean-square (RMS) amplitude.
 10. The system of claim 1, furthercomprising: an exciter, configured to receive the excitation signal fromthe controller and to provide to the primary winding the sinusoidalexcitation waveform having the excitation frequency; the sensor; and theADC.
 11. A method of determining position of a movable component bycalculating an amplitude of a sinusoidal output waveform from a sensor,the method comprising: providing, by a controller, an excitation signalhaving an excitation frequency to an exciter; providing, by thecontroller, a sample signal having a sample frequency that is four timesthe excitation frequency, to an analog-to-digital converter (ADC),supplying, by the exciter, a sinusoidal excitation waveform having theexcitation frequency to a primary winding, wherein: the primary windingis inductively coupled to a secondary winding in such a manner that theinductive coupling changes in response to movement of the movablemember; the secondary winding is configured to produce the sinusoidaloutput waveform when the sinusoidal excitation waveform is supplied tothe primary winding; and the secondary winding is configured to inputthe sinusoidal output waveform to an ADC; measuring, by the ADC, a firstvoltage of the sinusoidal output waveform and a second voltage of thesinusoidal output waveform, the second voltage measurement occurring ata time corresponding to a period of the sample frequency following thefirst voltage measurement; calculating, by the controller, the amplitudebased on the measurements of the first and second voltage; anddetermining, by the controller, a position of a movable component basedon the amplitude of the sinusoidal output waveform calculated, whereinthe primary winding and the secondary winding comprise the sensor. 12.The method of claim 11, wherein: the sensor is a linear variabledifferential transformer (LVDT); and the sensor is configured to measurea linear position of a linear component mechanically connected thereto.13. The method of claim 12, wherein the amplitude is representative ofthe linear position.
 14. The method of claim 11, wherein the sensor is aresolver further comprising a tertiary winding, wherein: the primarywinding is rotatable; the secondary winding is fixed relative to theprimary winding; the tertiary winding is fixed relative to the primarywinding and positioned out of phase with respect to the secondarywinding; and the sensor is configured to measure an angular position ofa rotatable component mechanically connected thereto.
 15. The method ofclaim 14, wherein the tertiary winding is positioned π/2 radians out ofphase with respect to the secondary winding.
 16. The method of claim 14,wherein the amplitude is representative of the angular position of therotary component.
 17. The method of claim 11, wherein the excitationfrequency is between 400-5,000 Hz.
 18. The method of claim 11, whereinthe excitation frequency is between 2,000-3,500 Hz.
 19. The method ofclaim 11, wherein the sinusoidal excitation waveform further comprises apeak amplitude between 5-12 volts.
 20. The method of claim 11, whereinthe amplitude is a root-mean-square (RMS) amplitude.